1. Field of the Invention
The present invention relates to a magnetic disk drive apparatus with a plurality of magnetic head sliders.
2. Description of the Related Art
A magnetic disk drive apparatus has in general a single disk or a plurality of magnetic disks and a plurality of magnetic head sliders each having a thin-film magnetic head with a magnetoresistive effect (MR) read head element and an inductive write head element. Two magnetic head sliders face in operation a front surface and a back surface of each magnetic disk, respectively.
There is a magnetic disk drive apparatus with a load/unload mechanism for retracting the magnetic head from the magnetic disk upon non-operation and for putting the magnetic head back on the magnetic disk upon operation, in order to enhance the resistance to shock externally applied.
Some magnetic disk drive apparatuses with such load/unload mechanisms apply magnetic field to the unloaded magnetic head so as to suppress Barkhausen noise of the MR read head element from occurring and to reduce read errors. Japanese patent publication No. 2002-150510A and U.S. patent publication No. 2006/0023366A1 disclose magnetic disk drive apparatuses having magnetic field application mechanisms at their ramp portions for applying magnetic field to the unloaded magnetic heads in order to re-magnetize their read head elements.
However, according to such magnetic disk drive apparatus disclosed in Japanese patent publication No. 2002-150510A and U.S. patent publication No. 2006/0023366A1, the magnetic field in a single direction is applied from the magnetic field application mechanism to both the magnetic head sliders mounted to face the front surface and back surface of the magnetic disk in operations. Therefore, for each magnetic head slider located at the front surface side or the back surface side, the magnetic field in the opposite direction to each other is applied. Thus, it is necessary to mount, at the front surface side and the back surface side, two kinds of magnetic head sliders with opposite magnetization directions for magnetically stabilizing their magnetization-free layers. In other words, according to the conventional magnetic disk drive apparatus, necessary is to prepare two types of magnetic head with different magnetic bias directions causing the versatility of magnetic head to extremely deteriorate.